This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A133947 #13 Sep 16 2015 13:43:59 %S A133947 2,3,4,4,5,5,4,6,7,4,6,6,4,8,8,4,5,5,6,11,7,4,6,8,4,5,8,4,7,7,4,8,5,4, %T A133947 15,6,4,5,10,6,7,7,4,12,9,4,6,9,4,7,8,4,5,10,10,9,5,4,8,8,4,7,10,6,9, %U A133947 5,4,6,10,4,8,8,4,7,10,4,11,5,6,13,5,4,8,15,4,5,8,4,9,13,6,6,5,4,12,6,4,9 %N A133947 a(n) = the number of "non-isolated divisors" of n(n+1). A positive divisor, k, of n is non-isolated if (k-1) or (k+1) also divides n. %H A133947 Ray Chandler, <a href="/A133947/b133947.txt">Table of n, a(n) for n=1..10000</a> %F A133947 a(n) = A092517(n) - A133948(n) = A132747(A002378(n)). %t A133947 Table[Length[Select[Divisors[n*(n + 1)],If[ # > 1, Mod[n*(n + 1), #*(# - 1)] == 0] || Mod[n*(n + 1), #*(# + 1)] == 0 &]], {n, 1, 80}] (* _Stefan Steinerberger_, Nov 01 2007 *) %Y A133947 Cf. A133948, A133949, A092517. %K A133947 nonn %O A133947 1,1 %A A133947 _Leroy Quet_, Sep 30 2007 %E A133947 More terms from _Stefan Steinerberger_, Nov 01 2007 %E A133947 Extended by _Ray Chandler_, Jun 23 2008